In general, in analytical systems aliquots of a reagent or medium must be prepared in micro-quantities. Biochemical procedures also use plates, hereinafter referred to as microbeaker plates, having orthogonal rows of cup-shaped cavities or recesses of limited depth and limited volumetric capacity into which it is desired to dispense small but equal quantities of a liquid. The microcups cooperate with a corresponding number of storage vessels which contain a liquid and are connected to
tubes aligned with the microcups. By increasing the pressure above the liquid level within each storage vessel, the liquid is discharged from the latter into the aligned microcup.
Such an apparatus, which may be referred to as a "dispensing device" or "dispenser" is marketed by Dynatech Produkte AG, Kloten (Switzerland) under the tradename "AM 160 MIC-2000" and can be used to fill 96 microcups of a microcup or microbeaker plate, e.g. the Microtiter.sup.(R) plate. The dispensing device includes a test tube rack with 96 open test tubes from which transfer tubes extend to a dispensing head provided with 96 individual valves and having outlet openings opposite to the 96 microcups of the plate. The test tubes are accommodated in an enclosed space whereby the transfer tubes project through appropriate seals towards the exterior. Leading into the space is a pipe connected to a compressor and including a regulator for increasing the pressure above the test tubes.
Through controlled pressure increase, liquid can be forced out of the test tubes to the dispenser head via the transfer tubes. The valves are simultaneously opened and closed by a separate control mechanism so that a requisite liquid quantity is discharged into each of the microbeakers.
This commercial product is complicated to control and operate and is also relatively expensive.